Several types of mass and heat exchanger or "vapor pump" are already known which enable a greater or lesser fraction of the sensible and the latent heat contained in the combustion products leaving a condensation generator to be recycled with the combustion air required by the thermal process.
Thus, Document FR-B-2 446 460 proposes a condensation heating installation including a heat exchanger/regenerator for thermally coupling the combustion air required by the heat generator and the combustion products from the heat generator, with humidifier means being provided to extract at least a portion of the condensates from the combustion products and to put these condensates into contact with the combustion air. This prior heat exchanger comprises a plurality of juxtaposed compartments separated by vertical partitions and communicating at their ends with bottom and top chambers, a first series of alternate compartments having their first ends in communication with a first bottom chamber and their second ends in communication with a first top chamber, while the compartments immediately adjacent to the alternate compartments of the first series are in communication with a second top chamber via their ends close to said first ends and with a second bottom chamber via their ends close to said second ends. The alternate compartments in communication with the first top and bottom chambers have air to be reheated flowing through them, while the alternate compartments in communication with the second top and bottom chambers have combustion products flowing through them. A first series of condensate feed strips is installed at the top end of the compartments in the second series while a second series of condensate feed strips is installed at the top end of the compartments in the second series. If it is desired to obtain high efficiency, a heat and mass exchanger of this type turns out to be expensive, difficult to implement, and very bulky. In addition, it is designed to provide cross-flow exchange, and most of the time it leads to the flue gases being humidified excessively or to a phenomenon of condensate running down both sides of the exchanger walls, which often reduces heat exchanger efficiency. In general, it is difficult to control the condensates, and in any case auxiliary pumping or blowing installations consume energy in amounts that are often not negligible.
Proposals have also been made in Document FR-A-2 508 616 for a device that treats gases that are relatively hot and moist, e.g. flue gases, and gases that are relatively dry and cool, e.g. oxidizer gases for a hearth, for the purpose of recovering the heat and possibly the condensates from the flue gases and reheating and humidifying the combustion air. However, this prior treatment device uses two distinct enclosures, one having the hot moist gases passing therethrough while the other has the relatively dry and cool gases passing therethrough, with each of the enclosures including means at its top for spraying liquids constituted by the condensates recovered during the treatment. Here again, the treatment device is bulky because of the presence of two enclosures, and although its efficiency is acceptable, it is nevertheless limited. In addition, such an installation requires means to be implemented for balancing the flow rates through the various enclosures together with fluid transfer means (circulation pumps, blowers) that may give rise to considerable energy consumption related, in particular, to gas flow headlosses in the two enclosures, each of which is filled with metal packing.
The present invention seeks to remedy the above-mentioned drawbacks and to obtain higher efficiency when recycling the enthalpy of combustion products by using a heat and mass exchanger which is small in size and cheap to manufacture and operate.
Another object of the invention is to provide a heat and mass exchanger or "vapor pump" capable of being used in combination with various thermal processes that may or may not be associated with condensers and without it being necessary to proceed with difficult adaptations, particularly in the case of large installations such as boiler plants using condensation boilers.